Ha, yea, talk about discoverability! I talked a bit about this with someone in the World of MULE discord server. I have an idea to allow for collusion again: since horizontal controller movement is not used, I think I can introduce an interface that will allow players to indicate they wish to collude with a specific other player. And if the other player reciprocates, collusion occurs as it used to do. Depending on how I present it, it may only be a smidge more discoverable than before, but it'll improve upon how people used to have to count out (1... 2... 3... press!).
Excellent! I wonder if collusion was in the game documentation from back then… Looks like it was, makes sense it was tournament only: http://muttoo.on.ca/mulemanual/